Kate Middleton's 10 years of royal style fall into four broad categories: business casual duchess, summer duchess, sporty duchess, and formal duchess (she's like a one-woman Spice Girls).

The formulas are as follows: business casual: tailored pants, blouse, blazer, pointy heel pumps. Summer is sundresses, wedge sandals or tennis shoes. Sporty is clothing appropriate for sports.

As for formal, the Duchess usually wears a monochromatic uniform (which allows her to stand out in a crowd), a court dress from her favorite designer, sometimes paired with a fascinator or clutch bag, and another pair of her trusty pointy-heeled pumps.

The Duchess of Cambridge attended the Garter Day service at Windsor Castle in what I call pansy blue. She wore a fascinator in the same color by Juliette Botterill Millinery, a scalloped clutch bag, and pointy blue slingback pumps by Aquazzura.

The Duchess matched her iconic engagement ring with blue jewelry by G. Collins & Sons.

Several items from her look can be purchased below.

Garter Day, also known as the Order of the Garter service, honors members of the Order of the Garter who are chosen for their dedication to public service. On this day, the queen and several senior royalty wear intricate velvet robes and march in grand procession. It will come as no surprise to learn that this tradition began in 1348.